Polyolefins, as a class of materials, have relatively poor adhesion and compatibility with more polar polymeric materials. In most cases, a separate adhesive is required in order to adhere polyolefins to polar substrates like polyesters, polyamides, and polyurethanes. Similarly, a third component compatibilizer typically has to be used to prepare satisfactory melt blends of polyolefins with other more polar thermoplastics.
Thermoplastic polyolefins, due to their nonpolar nature, generally lack adhesion to polar materials, such as polyurethanes. Thus, a flexible thermoplastic olefin sheet is conventionally surface treated with a primer solution containing one or more polar compounds to increase the adhesion to a polyurethane surface. Typical primer solutions contain a chlorinated maleated polyolefin. Such a surface treatment requires a large ventilation area, equipped to handle sheeting through a gravure application; a primer application mechanism, such as a dip tank; and a drying means to flash off the water and other solvent carriers. In addition, a flexible thermoplastic olefin skin must adhere, without voids and other visible defects, to the polyurethane foam. The polyurethane foam should adhere to the thermoplastic polyolefin surface, without delamination at the interface (or adhesive failure). A discontinuous application of a primer solution may lead to the formation of voids between the thermoplastic olefin skin and polyurethane foam in areas that lack the primer. Surface voids are a costly problem for manufacturers, since parts that have surface voids cannot be used in an automotive assembly, and are instead scraped.
Polymeric sheeting for certain consumer end product applications may have to meet several end-use requirements. Requirements may include a low gloss value, a high surface scratch/mar resistance, high heat resistance, and a good cold temperature impact resistance. In addition, polymeric sheeting may be required to have good adhesion to an intermediate polyurethane (PU) foam layer, for example a foam layer used to provide a softening or cushioning effect.